Underwater hydrodynamic acoustic projector



Sept. 24, 1968 R. H. MELLEN ETAL 3,403,374

UNDERWATER HYDRODYNAMIC ACOUSTIC PROJECTOR Filed April 5, 1962 BY M3,403,374 UNDERWATER HYDRODYNAMIC ACOUSTIC PROJECTOR Robert H. Mellen,Old Lyme, Robert Berman, New London, and Kenneth L. Moothart,Stonington, Conn., assignors to the United States of America asrepresented by the Secretary of the Navy Filed Apr. 5, 1962, Ser. No.185,489 1 Claim. (Cl. 340-8) ABSTRACT OF THE DISCLOSURE An underwateracoustic energy projector having two oppositely directed planar pistonsmounted in the opposite ends of a tubular housing, hydraulic motor meansin the housing, and hydraulic conduits extending from the hydraulicmotor means through the wall of the tubular housing for transmittingdriving force to the planar pistons forcing them to execute mirror imagedisplacement. The perimeters of the pistons are yieldably secured to thehousing by elastomeric means to form a fluid tight structure.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties there-on or therefor.

An object of this invention is to provide a more rugged underwateracoustic wave projector.

A further object is to provide a high power underwater acoustic waveprojector that has a smaller ratio of overall volume to power handlingcapacity relative to other units available heretofore for this purpose.

A further object is to provide an underwater acoustic wave generatorthat is flexible in operation and can be used to impart power to thewater in the character of a single hammer-like pulse, a singleimplosion-like pulse, spaced apart periodic pulses, continuous duty,nondescript noise, or message bearing waveforms.

A further object is to provide an underwater acoustic wave projectorthat is not readily damaged by rough handling, is of simpleconstruction, does not require delivery of electric power underwater, isof comparatively low cost to construct and operate, and is readilyadaptable to very high power applications.

Other objects and advantages will appear from the following descriptionof an example of the invention, and the novel features will beparticularly pointed out in the appended claim.

FIG. 1 is a simplified longitudinal sectional view of a hydraulicallyoperable underwater sound projector embodying the principles of thisinvention and not including ordinary details of construction, e.g.,seals, joints, fastenings, and FIG. 2 is a block diagram of ahydrodynamic system including a sound projector of the type shown inFIG. 1.

The hydraulic sound projector embodiment 10 shown in FIG. 1 includes atubular housing element 12 of rigid, tough material impermeable toseawater. Centrally located and rigidly mounted in the housing elementwith braces that are not shown on the drawing, is a hydraulic motor 14which includes two double-acting, substantially identical, drivingpistons 16L and 16R reciprocable in respective in-line cylinders 18L and18R in motor block 20. A pair of separate hydraulic conduits 22 and 24extend through and are sealed fluid tight in the wall of housing element12 and are in fluid communication with the remote ends and proximateends respectively of cylinders 18L and 18R. Identical radiating pistons26L and 26R are rigidly joined by connecting rods 28L and 28R to drivingpistons 16L and 16R. The effective areas of nited States Patent bothfaces of each double acting driving piston are made equal by theaddition of area compensation rods 30L and 30R that have cross sectionsequal to that of connect- 1ng rods 28L and 28R secured to and extendingfrom the faces of the driving pistons opposite to the faces joined tothe radiating pistons. The area compensation rods 30L and 30R are ofsuflicient length to extend beyond the inner ends of the cylinders 18Land 18R toward one another and are separated by an air space in themotor block 20. The perimeters of the radiating pistons 26L and 26R arejoined fluid tight to the ends of housing element 12 by compliantelastomeric annuli 32L and 32R. The interior of the housing element 12contains dry air. If intended for operation at shallow depth, air atatmospheric pressure or at the pressure corresponding to the operatingdepth occupies the housing element, but if the projector is intended foruse at greater depths, a static pressure head compensating apparatus maybe used. The pressure compensating system includes a differential valvesubject to the pressure inside and outside the housing element forbleeding air out of the housing element when the pressure differentialexceeds a preselected amount; the system also includes a compressed gasbottle and a valve responsive to pressure differential between exteriorand interior of housing element in excess of a preselected amount toopen and admit gas from the bottle into the housing element until thedifferential is reduced enough to close the valve.

The unit shown in FIG. 1 is recoilless because the reactions of the twohalves are equal and opposite. However, the invention may be practicedby constructing a unit having one radiating piston only, utilizing halfthe structure shown in FIG. 1. The latter requires reaction mass orrigid support structure. The structure disclosed may be readilyconstructed empirically to satisfy specifications such as operatingdepth and power handling capacity displacement, and the like.

The projector 10 is driven by a hydraulic pressure source 40 andreversing valve 42 as shown in FIG. 2 Suitable valves for this systemare the commercially available electrohydraulic servo units, such asthose made by Moog Valve Co. and Cadillac Company. Also valve mechanismsthat have been used in hydrodynamic shake table equipment of the typemanufactured by MB Electronics Company of New Haven, Conn., may be usedas reversing valve 42. A solenoid operated hydraulic reversing valve forswitching the hydraulic connections between the conduits 22 and 24 andthe pressure and return lines of the hydraulic pressure source 40 may beused. Regardless of the type of reversing valve selected, each time thevalve operates to reverse connections, the radiating pistons aredisplaced outwardly or inwardly. The acoustic wave projector 10 may belocated a considerable distance away from the reversing valve 42; as forexample when the projector is suspended from a ship into deep water atthe end of a supporting cable. In that case, the conduits 22 and 24 maybe flexible high pressure hoses.

This invention is of comparatively low cost to construct and operate,lends itself to very high power applications, is of simple construction,does not require delivery of electric power underwater, is rugged andcan readily absorb considerable abuse from rough handling and impactswith solid objects in the water without being damaged. Also, it iscompact and for a particular overall size and weight is capable ofdelivering more power to the water compared to other projectorsavailable heretofore. It lends itself readily to continuous dutyoperation or to impart one pulse to the water and it may be used togenerate acoustic noise or message bearing acoustic waveforms.

It will be understood that various changes in the details, materials andarrangements of parts (and steps), which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art within the principle and scope of theinvention as expressed in the appended claim.

We claim:

1. An underwater acoustic projector comprising a hydraulic motorincluding a pair of in-line identical cylinders,

identical driving pistons reciprocable in line in the respectivecylinders,

two pockets of hydraulic fluid occupying the interior of each cylinderon opposite sides of the respective driving pistons, the pockets ofliquid in each cylinder being isolated by the respective driving piston,

21 pair of in-line oppositely directed identical planarfaced radiatingpistons rigidly joined to the respective driving pistons and disposedexterior of the respective cylinders,

a tubular housing supporting the hydraulic motor therein and theradiating pistons across the ends within the housing,

elastomeric means yieldably joining the perimeters of the pistons andthe inside perimeters of the housing in fluid-tight relationship,

one conduit joined to the further apart interior portions of thecylinders,

another conduit joined to the closer interior portions of the cylinders,said conduits extending through the housing wall in water-tightrelationship therewith,

said conduits being filled with hydraulic fluid identical to thehydraulic fluid in the cylinders,

the interior volume of the housing not occupied by radiating pistons,hydraulic motor, and conduits eing occupied by gas,

hydraulic means coupled to the other ends of said conduits to transmitequal and opposite forces through the hydraulic fluid to the drivingpistons.

References Cited UNITED STATES PATENTS 929,623 7/1909 Nirenberg 116-272,896,588 7/1959 Haynes et al. 137623 3,056,104 9/1962 De Kansk et al.1l6l37 X RICHARD A. FARLEY, Primary Examiner.

